The present invention relates to a method for controlling a tire vulcanization, and especially relates to a method for stopping the vulcanization when sum of products of vulcanizing rates obtained on the basis of a tire temperature is equal to a predetermined value.
In the tire industry, in order to produce a tire having stable characteristics, a vulcanization method which could vulcanize the tire sufficiently has been strongly required. As for a conventional method for controlling the tire vulcanization, various methods have been proposed, for example, in U.S. Pat. No. 3,819,915, U.S. patent application Ser. No. 143,966 filed on Apr. 24, 1981 and Japanese Patent Laid-Open Publication No. 27,737/82.
In a method disclosed in U.S. Pat. No. 3,819,915, the tire vulcanization is stopped when sum of products of vulcanizing rates calculated on the basis of measured tire temperature during the tire vulcanization reaches a predetermined value. However, according to this known method, since a thermometer which is easy to be damaged must be inserted into a tire inner portion maintained at high-temperature and high-pressure for detecting the tire temperature during the vulcanization, the vulcanizing apparatus becomes complicated in construction and requires difficult operation for maintenance and preservation thereof such as a repair of the thermometer. Moreover, in the vulcanizing apparatus, a vulcanizing chamber thereof must be changed corresponding to the types of tires to be vulcanized. In this case, it is necessary to again attach the thermometer to the vulcanizing chamber after it was detached from the previously used chamber, and thus the operations mentioned above become much more complicated. Further, according to the method mentioned above, since it is necessary to keep the thermometer in the inner portion of the tire until the vulcanization is finished, a trace of a thermometer insertion is remained in a surface of the vulcanized tire.
In order to eliminate the drawbacks mentioned above, according to the method disclosed in the Japanese Laid-Open Publication No. 27,737/82, the thermometer is pulled out of the tire in the course of the vulcanization without measuring the tire temperature until the end of the vulcanizing operation. However, according to such a method, since the tire temperature must be measured until about the middle of the vulcanizing period, there also remains the drawbacks mentioned above due to the temperature measurement under the high-temperature and high-pressure states.
Moreover, in the U.S. Ser. No. 143,966, there is disclosed a method for controlling the vulcanizing period by measuring the temperature on outer and inner surfaces of tire without measuring directly the temperature of the inner portion of tire during the vulcanizing operation. According to this known method, the trace of the thermometer insertion is not remained on the tire surface after the vulcanization. However, since it is necessary to measure the tire temperature of the outer and inner surfaces during the vulcanization, there still remain the drawbacks that the vulcanizing apparatus becomes complicated in construction and requires the troublesome operation for the maintenance and the preservation thereof. Further, since the method mentioned above is to determine a vulcanizing end time of the tire by assuming the tire temperature during the vulcanization on the basis of thermal inputs from the outer and inner surfaces of the tire, a large error occurs in the measurement of the thermal input and thus the vulcanizing rate can not be controlled accurately.
As mentioned above in detail, according to the conventional methods for controlling the tire vulcanization, it is necessary to measure the tire temperature actually during the vulcanizing operation and thus there occurs the drawback that the maintenance of the thermometer exposed in the high-temperature and high-pressure condition becomes very complicated.